The present invention relates to a metal bonded diamond wheel. More particularly, the invention relates to a wheel having a sintered body of metal-bonded diamond suitable for grinding works of glass, ceramics, cermets and the like capable of exhibiting excellent grindability with low grinding resistance and long wear performance.
The grinding of glass, ceramics, cermets and the like materials in the prior art are performed mostly by using a metal-bonded diamond wheel in view of the excellent grindability and long wear performance. Such a diamond wheel has a structure composed of a metal base and a layer of a powder-metallurgically formed thereon from a mixture of a diamond powder and a metal powder to serve as a bonding material of the diamond particles. FIG. 1 illustrates a grinding wheel for edge rounder by a cross section as an example of such a metal-bonded diamond wheel, in which a layer of a sintered body 5 is provided in the cavity of a metal core 6.
Among various kinds of metals and alloys used as a metallic bonding material of a diamond powder, a particularly preferred is an alloy of copper and tin when the intended use of the diamond wheel is for grinding of glass, ceramics, cermets and the like. Diamond tools prepared by using an alloy of copper and tin as the metallic bonding material of diamond particles, however, have a disadvantage due to the relatively low holding power for the diamond particles that the durability of the wheel is low with relatively rapid wearing of the metal-bonding and the configuration of the grinding surface is subject to changes during use of the wheel although the grinding resistance is low to exhibit good sharpness of grinding as a consequence of rapid refreshing of the grinding surface because of falling of the abrasive diamond particles.
The holding power of the metallic bonding material for diamond particles can be improved by using nickel, cobalt, iron or an alloy of these metals as the bonding material. These metals and alloys, however, have a relatively high melting point so that sufficient sintering can be obtained only by performing the powder metallurgical sintering process at a high temperature of, for example, 900.degree. C. or higher while the diamond particles are rapidly graphitized at such a high temperature to cause a loss in the grinding power of the diamond particles. The grinding power of diamond particles can be maintained when the particles are coated with a metal of high melting point such as tungsten or an alloy of tungsten although this method is unavoidably accompanied by another problem that the grindability of wheel is decreased as a consequence of the high wearing resistance of the bonding.